Connection structure of steering torque transmitting member for steering shaft

ABSTRACT

A coupling structure for coupling a pair of steering torque transmitting members interposed in a steering shaft is arranged such that a steering torque is transmitted from one of the steering torque transmitting members to the other through a pin. One of the steering torque transmitting members has a pin insertion hole formed with a large diameter hole portion, a stepped receiving portion and a small diameter hole portion, while the pin has a large diameter portion, a stepped portion and a small diameter portion which are respectively engaged with the large diameter hole portion, the stepped receiving portion and the small diameter hole portion of the pin insertion hole.

TECHNICAL FIELD

The present invention relates to a coupling structure of torquetransmitting members for a steering shaft.

BACKGROUND ART

Various kinds of couplings are used in a steering apparatus of avehicle, including an elastic shaft coupling, which comprises an elasticmember of rubber interposed between, for example, a yoke of a universaljoint and a shaft to be inserted in this yoke, thereby absorbingvibration of an engine or a wheel to suppress transmission of thevibration to a steering wheel.

In such an elastic shaft coupling, a torque is transmitted from theshaft to the yoke through the elastic member in a range having a lowtorque. However, in a range having a high torque, the transmitting isperformed upon direct contact of a stopper face which is providedbetween the yoke and the shaft.

As shown in FIG. 7A, a stopper plate 3 formed with a cut-away portion 2and a disc-shaped elastic member 4 are secured to a steering shaft 1,and a flange 5 of an unrepresented yoke is attached to the shaft 1through a bush 6.

A pin 8 is inserted through the elastic member 4 and the flange 5 of theyoke through a washer 7. An end of the pin 8 on the yoke side is a malethread shaft which is thread-engaged with a nut 9 to be fixed. The otherend of the pin 8 is to be brought into contact (engagement) with thecut-away portion of the stopper plate 3.

Accordingly, in the range with low torque, the elastic member 4transmits, while being elastically deformed, a steering torque by itsdeforming resistance. On the other hand, in the range with high torque,the other end of the pin 8 transmits, while being brought into contact(engagement) with the cut-away portion 2 of the stopper plate 3, asteering torque directly to the shaft 1 from the flange 5 of the yoke.

Also in case of FIG. 7B, the structure for transmitting the steeringtorque is the same as that in the above-described case. However, the endof the pin 8 on the yoke side in this case is fixed to the flange 5 byclinching. In this case also, the pin 8 has a structure with two stepsin which it has a large diameter in its part fitted to the elasticmember 4 and a small diameter in its part fitted to the flange 5.

Also in case of FIG. 7C, the structure for transmitting the steeringtorque is the same as that in the above-described case. In this case,however, the elastic member 4 is integrally formed with the washer 7 andthe end of the pin 8 on the yoke side is fixed to the flange 5 byclinching. In this case also, the pin 8 has a structure with two stepsin which it has a large diameter in its part fitted to the elasticmember 4 and a small diameter in its part fitted to the flange 5.

Though not particularly illustrated, there may another structure forfixing the pin 8 to the flange 5 in which an unstepped pin is fixed byclinching or a stepped pin is fixed by a thread engaging means.

Incidentally, there is a demand for reinforcement of the strength of afixing structure between the pin 8 and the flange 5.

In such a case, the diameter of the pin 8 may be enlarged. In this case,however, there arise problems such that the weight thereof becomesgreater and that the diameter can not be enlarged when the pininterferes with peripheral components. Also in this case, the width ofthe cut-away portion 2 of the stopper plate 3 has to be increased, whichresults in an increased size of the whole structure in order to maintainthe strength. Further, the diameter of a pin insertion hole of theelastic member 4 has to be enlarged, which may resultantly lead to anenlarged size of the elastic member. Still further, the hole diameter ofthe flange 5 of the yoke has to be enlarged, which may resultantly leadto an enlarged size of the flange 5. When there is no enlargement of thesize or the reinforcement, the strength is deteriorated.

Still, there may be a case that the hardness of the pin 8 is reinforced.In such a case, however, a clinching work may become difficult toperform, or the structure may be easily affected by an impact load, orthe manufacturing cost may be widely increased due to an additionalthermal processing step of the materials.

SUMMARY OF THE INVENTION

The present invention has been contrived taking the circumstancesdescribed above into consideration and an object thereof is to provide acoupling structure of steering torque transmitting members for asteering shaft which is capable of enhancing the strength of a pinfixing structure, reducing the number of the constituent components, themanufacturing cost and the weight of the structure, and of improvingworking and assembling performance (that is, reducing the assemblingtime).

In order to achieve the above object, according to the presentinvention, there is provided a coupling structure of steering torquetransmitting members for a steering shaft for coupling a pair ofsteering torque transmitting members interposed in a steering shaft,characterized in that:

-   -   one of the steering torque transmitting members and the other of        the steering torque transmitting members are adapted to transmit        a steering torque through a pin;    -   the one of the steering torque transmitting members has a pin        insertion hole provided with a large diameter hole portion, a        stepped receiving portion and a small diameter hole portion; and    -   the pin has a large diameter portion, a stepped portion and a        small diameter portion which are respectively engaged with the        large diameter hole portion, the stepped receiving portion and        the small diameter hole portion of the pin insertion hole.

As described above, according to the present invention, one of thesteering torque transmitting members and the other of the steeringtorque transmitting members are adapted to transmit a steering torquethrough a pin, the one of the steering torque transmitting members has apin insertion hole provided with a large diameter hole portion, astepped receiving portion and a small diameter hole portion, and the pinhas a large diameter portion, a stepped portion and a small diameterportion which are respectively engaged with the large diameter holeportion, the stepped receiving portion and the small diameter holeportion of the pin insertion hole. Thus, the pin and the pin insertionhole respectively have stepped structures, so as to concentrate thestress on the large diameter portion. As a result, it is possible toenhance the strength of the pin fixing structure, to reduce the numberof the constituent components, the manufacturing cost and the weight ofthe structure, and to improve working and assembling performance (thatis, reducing the assembling time).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of the essential portion of a steeringapparatus for a car which incorporates therein a coupling structureaccording to an embodiment of the present invention;

FIG. 2A and 2B are cross-sectional views of a steering shaft, a yoke ofa universal joint, and an elastic shaft coupling interposedtherebetween, respectively according to different embodiments of thepresent invention;

FIG. 3A is a cross-sectional view of a coupling structure between a pinand a flange according to an embodiment of the present invention, andFIG. 3B is a cross-sectional view of a coupling structure between thepin and the flange according to the prior art;

FIGS. 4A, 4B and 4C are respectively cross-sectional views of differentcoupling structures between the pin and the flange according toembodiments of the present invention;

FIGS. 5A and 5B are respectively cross-sectional views of differentcoupling structures between the pin and the flange according toembodiments of the present invention;

FIG. 6A shows a cross-sectional view of the pin and that of a flangeaccording to an embodiment of the present invention, and FIG. 6B is across-sectional view of the pin and the flange shown in FIG. 6A, in astate that the pin and the flange are assembled; and

FIGS. 7A, 7B and 7C are respectively cross-sectional views of differentcoupling structures between the pin and the flange according to theprior art.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Description will be made on a steering apparatus for a vehicle whichincorporates therein an elastic shaft coupling employing a couplingstructure of steering torque transmitting members according to anembodiment of the present invention, with reference to drawings.

FIG. 1 is a side view of the essential portion of the steering apparatusfor a vehicle which incorporates therein the coupling structureaccording to an embodiment of the present invention.

As shown in FIG. 1, an intermediate shaft 103 is coupled to a lower endof a main shaft 101 which is coupled to a steering wheel (not shown)through an upper universal joint 102, while an input shaft 105 of a gearapparatus (not shown) is coupled to a lower end of the intermediateshaft 103 through a lower universal joint 104.

Description will be made below on a coupling structure of torquetransmitting members for a steering shaft according to an embodiment ofthe present invention, with reference to drawings.

Embodiments Shown in FIGS. 2A and 2B

FIGS. 2A and 2B respectively illustrate different embodiments of thepresent invention, representing cross-sectional views of a steeringshaft, a yoke of a universal joint, and an elastic shaft couplinginterposed therebetween.

As shown in FIG. 2A, the steering shaft 1 and the yoke 11 of theuniversal joint 11 are coupled to each other through an elasticuniversal joint.

A stopper plate 3 having a cut-away portion 2 which is open outward inthe radial direction and a disc-shaped elastic member 4 are secured tothe steering shaft 1, while a flange 5 of the yoke 11 is attached to theshaft 1 through a bush 6.

A pin 8 is inserted through the elastic member 4 and the flange 5through a washer 7. An end of the pin 8 on the side of the yoke 11 isfixed by clinching. Specifically, the washer 12 is attached to theflange 5 by welding, pressure contact, bolt fastening, bonding, or thelike, and the end of the pin 8 on the side of the yoke 11 is fixed byclinching through this washer 12.

The other end of the pin 8 is arranged to be brought into contact(engagement) with the cut-away portion of the stopper plate 3.

Accordingly, in a range with low torque, the elastic member 4 transmits,while being elastically deformed, a steering torque by its deformingresistance. On the other hand, in a range with high torque, the otherend of the pin 8 transmits, while being brought into contact(engagement) with the cut-away portion 2 of the stopper plate 3, asteering torque directly to the shaft 1 from the flange 5 of the yoke.

As to be described more specifically later, the flange 5 has a pininsertion hole which is formed with a large diameter hole portion, astepped receiving portion and a small diameter hole portion, while thepin 8 has a large diameter portion, a stepped portion and a smalldiameter portion which are respectively to be engaged with the largediameter hole portion, the stepped receiving portion and the smalldiameter hole portion of the pin insertion hole.

As shown in FIG. 2B, in the present embodiment, the pin insertion holeportion 4 a of the elastic member 4 is formed to be cylindrical, and thewasher 7, though not shown in the drawing, may or may not be used.

The flange 5 further has a pin insertion hole which is formed with alarge diameter hole portion, a stepped receiving portion and a smalldiameter hole portion, while the pin 8 has a large diameter portion, astepped portion and a small diameter portion which are respectivelycorresponding to the large diameter hole portion, the stepped receivingportion and the small diameter hole portion of the pin insertion hole.

Embodiments shown in FIGS. 3A and 3

FIG. 3A is a cross-sectional view of a coupling structure between a pinand a flange according to an embodiment of the present invention, whileFIG. 3B is a cross-sectional view of a coupling structure between thepin and the flange according to the prior art.

As shown in FIG. 3B, in case of the prior art, an end of a pin 8 withtwo steps is clinched to the flange 5. It is arranged such that stressis concentrated in portions enclosed with circles.

As shown in FIG. 3A, in an embodiment of the present invention, theflange 5 has a pin insertion hole which is formed with a large diameterhole portion 21, a stepped receiving portion 22 and a small diameterhole portion 23, while the pin 8 has a large diameter portion 31, astepped portion 32 and a small diameter portion 33 which arerespectively to be engaged with the large diameter hole portion 21, thestepped receiving portion 22 and the small diameter hole portion 23 ofthe pin insertion hole. Since the pin 8 and the pin insertion hole arerespectively in stepped structures as described above so that the stresscan be concentrated in the large diameter portion, it is possible toenhance the strength of the pin fixing structure.

In case of the present embodiment shown in FIG. 3A, the stressconcentrated portions enclosed with the circles are generated in thelarge diameter portion so that a stress value can be reduced and thestrength of the pin can be enhanced.

Since the outer side of the small diameter portion 23 of the flange 5 isembossing-shaped, the thickness of the flange 5 can be reduced.

Further, the large diameter portion 31 of the pin 8 is press fitted inthe large diameter hole portion 21 of the flange 5. However, though thesmall diameter portion 33 of the pin 8 is press fitted in the smalldiameter hole portion 23 of the flange 5 in the above case, it issuffice if only inserting the small diameter portion 33 therein (with aclearance).

F denotes a repeated load from the stopper plate 3. In case of thestructure shown in FIG. 3A, it is possible to further suppress flexureof the pin with respect to F.

Moreover, in case of the prior art shown in FIG. 3B, the top of the holefor clinching and the flange 5 overlap each other so that the rigidityor the strength thereof is decreased. However, in the presentembodiment, since the top of the hole for clinching and the flange 5 donot overlap each other, it is possible to obtain high rigidity andstrength.

Embodiments Shown in FIGS. 4A to 4C

FIGS. 4A, 4B and 4C are respectively cross-sectional views of couplingstructures between the pin and the flange according to differentembodiments of the present invention.

As shown in FIG. 4A, in the present embodiment, the flange 5 has a pininsertion hole which is formed with a large diameter hole portion 21, astepped receiving portion 22 and a small diameter hole portion 23, whilethe pin 8 has a large diameter portion 31, a stepped portion 32 and asmall diameter portion 33 which are respectively to be engaged with thelarge diameter hole portion 21, the stepped receiving portion 22 and thesmall diameter hole portion 23 of the pin insertion hole. Since the pin8 and the pin insertion hole are respectively in stepped structures asdescribed above so that the stress can be concentrated in the largediameter portion, it is possible to enhance the strength of the pinfixing structure.

As shown in FIG. 4B, the outer side of the small diameter portion 23 ofthe flange 5 may be embossing-shaped, so that the thickness of theflange 5 can be reduced.

As shown in FIG. 4C, an end of the pin 8 may be formed as a male threadshaft and may be thread engaged with and fixed by a nut 9.

Embodiments Shown in FIGS. 5A and 5B

FIGS. 5A and 5B are respectively cross-sectional views of couplingstructures between the pin and the flange according to differentembodiments of the present invention.

In case of the embodiment shown in FIG. 5A, the flange 5 has a pininsertion hole which is formed with a large diameter hole portion 21, astepped receiving portion 22 and a small diameter hole portion 23, whilethe pin 8 comprises a large diameter portion 31, a stepped portion 32and a small diameter portion 33 which are respectively to be engagedwith the large diameter hole portion 21, the stepped receiving portion22 and the small diameter hole portion 23 of the pin insertion hole.Since the pin 8 and the pin insertion hole are respectively in steppedstructures as described above so that the stress can be concentrated inthe large diameter portion, it is possible to enhance the strength ofthe pin fixing structure.

In addition, the outer side of the small diameter portion 23 of theflange 5 is embossing-shaped, so that the thickness of the flange 5 canbe reduced.

Further, the large diameter portion 31 of the pin 8 is press fitted inthe large diameter hole portion 21 of the flange 5. However, though thesmall diameter portion 33 of the pin 8 is press fitted in the smalldiameter hole portion of the flange 5, it is suffice if only insertingthe small diameter portion 33 (with a clearance) therein.

F denotes a repeated load from the stopper plate 3. In case of thestructure shown in FIG. 4A, it is possible to further suppress theflexure of the pin with respect to F.

In case of the embodiment shown in FIG. 5B, an inclined hole portion 24is formed between the stepped receiving portion 22 and the smalldiameter hole portion 23, and an inclined portion 34 corresponding tothe inclined hole portion 24 is formed between the stepped portion 32and the small diameter portion 33. Other arrangements in this embodimentare the same as those in the foregoing embodiments.

Embodiment Shown in FIGS. 6A and 6B

FIG. 6A is a cross-sectional view of a pin and that of a flangeaccording to an embodiment of the present invention, and FIG. 6B is across-sectional view of the pin and the flange shown in FIG. 6A, in astate that the pin and the flange are assembled.

In case of the embodiment shown in FIGS. 6A and 6B, the large diameterportion 31 of the pin 8 is press fitted in the large diameter holeportion 21 of the flange 5. However, though the small diameter portion33 of the pin 8 is press fitted in the small diameter hole portion ofthe flange 5, it is suffice if only inserting the small diameter portion33 therein(with a clearance).

Note that the length of the press fitted portion is preferably not lessthan 5% of the thickness of the flange plate, and most preferably notless than 30% thereof. An interference between the pin and the flangehole is not less than 0.005 mm, and most preferably in a range from 0.05to 0.5 mm. The length of the portion A (the distance from the steppedreceiving portion of the pin to the bottom of the clinching hole) inFIGS. 6A and 6B is not less than 0.5 mm, and is preferably not less than2 mm. A value which is recommended for clinching may be used as a valuefor the hardness of the thermal processing of the pin, which ispreferably in a range from HV 100 to HV 400. The diameter of the pressfitted portion of the pin is not less than φ4, and preferably in a rangefrom φ8 to φ20. When the maximum shearing stress acting on the pin inthe present embodiment is compared with that in the conventionalstructure by numerical analysis under the normal use condition, it isconfirmed that about 70% of the stress is decreased.

Note that the present invention is not limited to the foregoingembodiments, but can be altered in variable manners.

As described above, according to the present invention, one of thesteering torque transmitting members and the other of the steeringtorque transmitting members are adapted to transmit a steering torquethrough a pin, one of the steering torque transmitting members has a pininsertion hole which is formed with a large diameter hole portion, astepped receiving portion and a small diameter hole portion, and the pinhas a large diameter portion, a stepped portion and a small diameterportion which are respectively to be engaged with the large diameterhole portion, the stepped receiving portion and the small diameter holeportion of the pin insertion hole. Thus, the pin and the pin insertionhole respectively have stepped structures, so as to concentrate thestress on the large diameter portion. As a result, it is possible toenhance the strength of the pin fixing structure, to reduce the numberof the constituent components, the manufacturing cost and the weight ofthe structure, and to improve working and assembling performance (thatis, reducing the assembling time).

1. A coupling structure of steering torque transmitting members for asteering shaft for coupling a pair of steering torque transmittingmembers interposed in a steering shaft, characterized in that: one ofthe steering torque transmitting members and the other of the steeringtorque transmitting members are adapted to transmit a steering torquethrough a pin; said one of the steering torque transmitting members hasa pin insertion hole formed with a large diameter hole portion, astepped receiving portion and a small diameter hole portion; and saidpin has a large diameter portion, a stepped portion and a small diameterportion which are respectively engaged with the large diameter holeportion, the stepped receiving portion and the small diameter holeportion of the pin insertion hole.
 2. A coupling structure of steeringtorque transmitting members for a steering shaft according to claim 1,wherein said large diameter portion of the pin is press fitted in thelarge diameter hole portion of the pin insertion hole.
 3. A couplingstructure of steering torque transmitting members for a steering shaftaccording to claim 1, wherein said pin projected from said pin insertionhole is fixed to said one of the steering torque transmitting members byclinching or thread engaging means.
 4. A coupling structure of steeringtorque transmitting members for a steering shaft according to claim 2,wherein said pin projected from said pin insertion hole is fixed to saidone of the steering torque transmitting members by clinching or threadengaging means.